https://www.history.com/news/neutral-countries-world-war-ii?cmpid=email-hist-inside-history-2022-0 [login to see] 2&om_rid=&~campaign=hist-inside-history-2022-0516
It has always seemed to me that nations could only remain neutral if (1) they had the ability to inflict more pain than it was worth to make an enemy of them or (2) belligerent parties could benefit more from their neutrality than if was worth to fight them